The present invention relates to a fluid pressure control valve and a fluid control system which includes such a valve. More particularly, the invention concerns fluid valves and systems in which it is intended that two different fluids of which both may be liquid, both may be gas or one gas and one liquid are to be supplied under pressure from separate pressurised sources and in which the pressure of one fluid is controlled in proportion to the pressure of the other fluid.
With many simple fluid control systems which employ relatively inexpensive components and two different fluid lines (the fluids from which may be intended to be introduced from one into the other in predetermined proportions and these proportions are related to the pressure under which the fluids are supplied to their respective lines) it is unlikely that the means for pressurising the respective fluids, such as an electrically driven pump or compressor, will provide constant pressure outputs for the fluids (albeit that the pressure of these outputs may be adjustable). It will be apparent that if the pressurising means for one of the fluids fluctuates in its pressure output as compared with that for the other fluid, the desired proportions in which the fluids may be introduced to each other will also fluctuate with possible undesirable consequences. This is particularly so for the dispensing of beverages such as beer, stout, lager, wine or so-called soft drinks where the beverage is supplied under pressure through one line to a dispensing tap while gas such as air, carbon dioxide or nitrogen is supplied under pressure through another line to be introduced into the beverage. The gas which is introduced may serve to form or to assist in the formation of a head on the beverage or to provide a sparkling or effervescent effect on the beverage as dispensed. In such dispensing systems the proportion of gas which is introduced should be maintained within a predetermined range for a given volume of the beverage as dispensed to ensure that neither too much gas is introduced which may result in the beverage having too great a head or effervescence or too little gas is introduced which may result in the bevrrage being "flat". It is an object of the present invention to provide a relatively inexpensive and simple fluid pressure control valve and a fluid control system by which the aforementioned undesirable features may be alleviated.